Pineapple contains bromelain, an enzyme that breaks down proteins—including the protective lining of your mouth—creating that distinctive tingling sensation when you eat it.

Bromelain is a complex mixture of protease enzymes found in the fruit and stems of the pineapple plant, Ananas comosus. These enzymes are specifically designed to break down proteins by cleaving the peptide bonds that link amino acids together. Since the human mouth is lined with sensitive tissues made of protein and collagen, bromelain begins to break down these surfaces on contact, causing the characteristic stinging or burning sensation many people experience when eating fresh pineapple. This is a chemical reaction, not an allergic response.The human body is remarkably resilient—cells in the mouth regenerate quickly to repair any minor surface damage caused by the fruit. Bromelain is so effective at breaking down organic matter that it's widely used commercially as a meat tenderizer. Industrial workers who handle pineapples often wear gloves and masks to prevent the enzyme from eroding their skin over time. However, the enzyme poses no danger when consumed because the highly acidic environment of the human stomach—with a pH between 1.5 and 3.5—denatures bromelain almost instantly.Research published in journals like Biotechnology Research International shows that bromelain has been studied since the late 19th century for its therapeutic properties. While it can make your tongue sore, it also offers anti-inflammatory and digestive benefits when processed by your body. Cooking or canning pineapple deactivates the enzyme through heat, which is why canned pineapple doesn't produce the same tingling sensation.